<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>for-in</title>
    <script src="../js/demo2.js"></script>
    <style>
        .items {
            display: inline-block;
            width: 30px;
            height: 30px;
            text-align: center;
            line-height: 30px;

        }
    </style>
</head>

<body>
    <div id="app"></div>
</body>

</html>